Re: [casper] Solar Spectrometer Channeliser

[Colm Bracken]

Hi All,

Thanks everyone for all the excellent advice!
I think we are going to try the 14-bit Red Pitatya for this, and just work
to the highest frequencies that we can achieve with the ADCs in the Nyquist
limit (namely 62 MHz).
I might eventually have a go at interleaving the two ADC channels to double
the sampling.

I'll update CASPER with any interesting results from this in the future.

Best wishes,
Colm

On Tue, 11 Feb 2020 at 06:05, Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> wrote:

> Hello Tavi,
>
> There are implementations of red pitaya as a SDR by Pavel Demin, but the
> max. bandwidth (that he has implemented) is about 2.5 MHz and also is
> limited in tuning range.
>
> Yes, using SDRs is another option. LimeSDR is a possible candidate which
> gives tunability and max. instantaneous bandwidth of ~ 60 MHz. It also has
> an Intel (Altera) FPGA, which people have tried to program to do some DSP
> as well.
>
> So this is a good suggestion.
>
> Sincerely,
>
> Mugundhan
>
>
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> 
> .
>


-- 

*Dr Colm Bracken*
Lecturer
Maynooth University Experimental Physics


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And


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Re: [casper] Solar Spectrometer Channeliser

[Tavi B]

Hi,

Thank you for your reply!

I would consider LimeSDR or maybe XTRX, it have a GPS onboard and PCI-ex
interface.

Best regards,

Tavi


În mar., 11 feb. 2020 la 08:05, Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> a scris:

> Hello Tavi,
>
> There are implementations of red pitaya as a SDR by Pavel Demin, but the
> max. bandwidth (that he has implemented) is about 2.5 MHz and also is
> limited in tuning range.
>
> Yes, using SDRs is another option. LimeSDR is a possible candidate which
> gives tunability and max. instantaneous bandwidth of ~ 60 MHz. It also has
> an Intel (Altera) FPGA, which people have tried to program to do some DSP
> as well.
>
> So this is a good suggestion.
>
> Sincerely,
>
> Mugundhan
>
>
> --
> You received this message because you are subscribed to the Google Groups "
> casper@lists.berkeley.edu" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to casper+unsubscr...@lists.berkeley.edu.
> To view this discussion on the web visit
> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAD560xnA8fo4sDZnzP%2BuvmO%2BbPahiau-xCOhEt%3DRdUV6tfsgiw%40mail.gmail.com
> 
> .
>

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Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Hello Tavi,

There are implementations of red pitaya as a SDR by Pavel Demin, but the
max. bandwidth (that he has implemented) is about 2.5 MHz and also is
limited in tuning range.

Yes, using SDRs is another option. LimeSDR is a possible candidate which
gives tunability and max. instantaneous bandwidth of ~ 60 MHz. It also has
an Intel (Altera) FPGA, which people have tried to program to do some DSP
as well.

So this is a good suggestion.

Sincerely,

Mugundhan

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Re: [casper] Solar Spectrometer Channeliser

[Tavi B]

t; available to him.
>>>>
>>>> What you're saying is true. Doing it with a single stage may be
>>>> problematic as with 20 MHz LO, the there will be overlap of the side bands.
>>>> So, minimally, we need to have two stages. where the 20-80 MHz can be
>>>> up-converted to outside the band and then down-converted into the base band
>>>> of 0-60 MHz.
>>>>
>>>> Sorry for not being clear earlier.
>>>>
>>>> But anyway, for the RedPitaya, due to the sampling restrictions, 20-80
>>>> MHz band has to be got into 0-60 MHz for getting the full band with the
>>>> board.
>>>>
>>>> Thank you,
>>>>
>>>> Mugundhan
>>>>
>>>> On Mon, Feb 10, 2020 at 2:32 PM Ross Martin 
>>>> wrote:
>>>>
>>>>> Hi Mugundhan,
>>>>>
>>>>> Could you say a little more about how you're downconverting 20-80MHz
>>>>> to 0-60MHz?  My understanding is that this is not easy to do while
>>>>> retaining signal quality.  The band overlap of the input and output bands
>>>>> means simple conversion methods with normal mixers don't work.
>>>>>
>>>>> Ross
>>>>>
>>>>>
>>>>> On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
>>>>> v.vaishnav151...@gmail.com> wrote:
>>>>>
>>>>>> Hi jishnu,
>>>>>>
>>>>>> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to
>>>>>> use the band fully. As such, it has a cutoff at 65MHz.
>>>>>>
>>>>>> Thanks,
>>>>>> Mugundhan
>>>>>>
>>>>>> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T, 
>>>>>> wrote:
>>>>>>
>>>>>>> Hi Mugundhan,
>>>>>>>
>>>>>>> With red pitaya, can you sample 20-80 MHz without downconversion ?
>>>>>>> And if analog down conversion is required, wouldn't that restrict the
>>>>>>> usable dynamic range (unless a high level mixer is used) ?
>>>>>>>
>>>>>>> Jishnu
>>>>>>>
>>>>>>> --
>>>>>>> *From: *"Mugundhan vijayaraghavan" 
>>>>>>> *To: *"casper" 
>>>>>>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>>>>>>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>>>>>>
>>>>>>> Hi Dan,
>>>>>>>
>>>>>>> We have done integration times from 20ms upto a second. There are
>>>>>>> bursts that last for hours, minutes and a few ms to seconds as well.
>>>>>>>
>>>>>>> We have not tried AGC on these bursts since we were aiming to study
>>>>>>> them only. In the 8 bit design, we had 3 bits for background and 
>>>>>>> remaining
>>>>>>> 5 to accommodate bursts.
>>>>>>>
>>>>>>> The red pitaya can still be used if Colm can restrict the band to
>>>>>>> 20-80 mhz, because the ionosphere starts cutting of anything below 20mhz
>>>>>>> mostly(depending on the location of course). Then this can be down
>>>>>>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Mugundhan
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Wed, 5 Feb 2020, 22:23 Dan Werthimer, 
>>>>>>> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>> hi mugundhan,
>>>>>>>>
>>>>>>>> what's the time scale for these bursts?
>>>>>>>> rise and fall times?
>>>>>>>> can you use a AGC circuit (automatic gain control),
>>>>>>>> eg: computer controlled attenuator
>>>>>>>> to turn down the power going into the ADC during the bursts,
>>>>>>>> so you could keep the levels going into the ADC relatively
>>>>>>>> constant?
>>>>>>>> if the rise and fall times are longer than 1ms (the integration
>>

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

 do while retaining
>>>> signal quality.  The band overlap of the input and output bands means
>>>> simple conversion methods with normal mixers don't work.
>>>>
>>>> Ross
>>>>
>>>>
>>>> On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
>>>> v.vaishnav151...@gmail.com> wrote:
>>>>
>>>>> Hi jishnu,
>>>>>
>>>>> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to
>>>>> use the band fully. As such, it has a cutoff at 65MHz.
>>>>>
>>>>> Thanks,
>>>>> Mugundhan
>>>>>
>>>>> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T, 
>>>>> wrote:
>>>>>
>>>>>> Hi Mugundhan,
>>>>>>
>>>>>> With red pitaya, can you sample 20-80 MHz without downconversion ?
>>>>>> And if analog down conversion is required, wouldn't that restrict the
>>>>>> usable dynamic range (unless a high level mixer is used) ?
>>>>>>
>>>>>> Jishnu
>>>>>>
>>>>>> --
>>>>>> *From: *"Mugundhan vijayaraghavan" 
>>>>>> *To: *"casper" 
>>>>>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>>>>>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>>>>>
>>>>>> Hi Dan,
>>>>>>
>>>>>> We have done integration times from 20ms upto a second. There are
>>>>>> bursts that last for hours, minutes and a few ms to seconds as well.
>>>>>>
>>>>>> We have not tried AGC on these bursts since we were aiming to study
>>>>>> them only. In the 8 bit design, we had 3 bits for background and 
>>>>>> remaining
>>>>>> 5 to accommodate bursts.
>>>>>>
>>>>>> The red pitaya can still be used if Colm can restrict the band to
>>>>>> 20-80 mhz, because the ionosphere starts cutting of anything below 20mhz
>>>>>> mostly(depending on the location of course). Then this can be down
>>>>>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Mugundhan
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, 5 Feb 2020, 22:23 Dan Werthimer, 
>>>>>> wrote:
>>>>>>
>>>>>>>
>>>>>>> hi mugundhan,
>>>>>>>
>>>>>>> what's the time scale for these bursts?
>>>>>>> rise and fall times?
>>>>>>> can you use a AGC circuit (automatic gain control),
>>>>>>> eg: computer controlled attenuator
>>>>>>> to turn down the power going into the ADC during the bursts,
>>>>>>> so you could keep the levels going into the ADC relatively
>>>>>>> constant?
>>>>>>> if the rise and fall times are longer than 1ms (the integration time
>>>>>>> of the spectrometer),
>>>>>>> then you could adjust the power level for each spectrum, and write
>>>>>>> down where
>>>>>>> you set the attenuator for that spectrum, so you could still know
>>>>>>> the absolute power.
>>>>>>>
>>>>>>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the
>>>>>>> new RFSOC boards/chips have 14 bit ADC's,
>>>>>>> but you'll have to write a casper yellow interface block for this
>>>>>>> ADC,
>>>>>>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>>>>>>
>>>>>>> another possiblity is to multiplex your 80 MHz band, 40 MHz at a
>>>>>>> time into a red pitaya board,
>>>>>>> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms,
>>>>>>> then 40 to 80 MHz for the next ms.
>>>>>>>
>>>>>>>
>>>>>>> best wishes,
>>>>>>>
>>>>>>> dan
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Wed, Feb 5, 2020 at 8:33 AM Mugund

Re: [casper] Solar Spectrometer Channeliser

[Ross Martin]

Hi Mugundhan,

If you have a single stage mixer with an LO at 80MHz, it has the problem
that the effective mixer signal may not be just a sine wave, but instead a
sine wave with a tiny DC offset.

If you have a DC offset that's X dB down from the sine wave amplitude, it
will pass the original signal through at a level X dB down.  You need to be
very careful that X is enough to provide the performance you desire,
because the original signal is on top of your output signal and will
interfere with it if it's not adequately attenuated.

The mixer will also have distortion. That distortion will cause 2nd, 3rd,
and higher-order effects, that need to be considered regarding what their
amplitudes might be and in what frequency ranges they are.

With more widely separated input and output frequencies for the mixer, it's
easier to arrange that all these undesired mixer outputs are at frequencies
that don't matter and can be rejected with lowpass or bandpass filters. In
your case, a lot of these error terms will be right on top of your signal,
and thus can't be rejected with a filter. That's probably not a problem if
you only need 10dB, but if you want quality signals it should be analyzed
carefully based on the specs of your mixer and your desired performance.
It may be that available mixers are really, really good, but it's something
that should be checked carefully.

Another issue with what you've proposed is that your output band goes all
the way down to 0 Hertz. Mixers may produce a lot of noise near 0 Hertz,
from squaring and quadratic distortion terms that effectively perform an AM
detection on your entire input signal. Because of this noise, you probably
don't want your signal going all the way down to zero Hertz, but instead
have it bounded away from zero by some small amount with at least a DC
rejection filter.  I'm not sure offhand how much separation might be
enough.  This problem will also affect multi-stage mixers.  It may be that
the mixer quality is good enough that this effect is small, but it should
be checked carefully.

Another issue you need to consider is that signals cannot cut off instantly
in the frequency domain.  They must have tails that fade off gradually. And
if you've got a sine wave at 1Hz, it's tails are most likely not going to
fade off below desired levels by 0Hz.  Almost no analog filters are that
good. Instead the tails will go past 0Hz into negative frequencies.  For
real signals, negative frequencies fold back into positive frequencies and
cause interference.  For this reason also, I believe your signal must be
strictly bounded away from 0Hz.

Regards,

Ross


On Mon, Feb 10, 2020, 8:26 AM Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> wrote:

> Hi Ross,
>
> Just to add, we can also have the lo at 80mhz, and use the lower side
> band. 80 will be at 0, 20 will be at 60. But the band can be flipped
> offline.  We can have a strong lpf at 60mhz, which can  cut the lo off
> before downstream processing.
>
> Mugundhan
>
> On Mon, 10 Feb 2020, 15:18 Mugundhan vijayaraghavan, <
> v.vaishnav151...@gmail.com> wrote:
>
>> Hi Ross,
>>
>> I'm not working with Colm on this. So I don't know about the resources
>> available to him.
>>
>> What you're saying is true. Doing it with a single stage may be
>> problematic as with 20 MHz LO, the there will be overlap of the side bands.
>> So, minimally, we need to have two stages. where the 20-80 MHz can be
>> up-converted to outside the band and then down-converted into the base band
>> of 0-60 MHz.
>>
>> Sorry for not being clear earlier.
>>
>> But anyway, for the RedPitaya, due to the sampling restrictions, 20-80
>> MHz band has to be got into 0-60 MHz for getting the full band with the
>> board.
>>
>> Thank you,
>>
>> Mugundhan
>>
>> On Mon, Feb 10, 2020 at 2:32 PM Ross Martin  wrote:
>>
>>> Hi Mugundhan,
>>>
>>> Could you say a little more about how you're downconverting 20-80MHz to
>>> 0-60MHz?  My understanding is that this is not easy to do while retaining
>>> signal quality.  The band overlap of the input and output bands means
>>> simple conversion methods with normal mixers don't work.
>>>
>>> Ross
>>>
>>>
>>> On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
>>> v.vaishnav151...@gmail.com> wrote:
>>>
>>>> Hi jishnu,
>>>>
>>>> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to
>>>> use the band fully. As such, it has a cutoff at 65MHz.
>>>>
>>>> Thanks,
>>>> Mugundhan
>>>>
>>>> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T, 
>>>> wrote:
>>>>
>>>>> Hi M

Re: [casper] Solar Spectrometer Channeliser

[Jishnu Nambissan T]

Hi Hari, 

Good point regarding RFI below 25 MHz, though in coming years more and more AM 
stations may go off air ! It may be hard to find high quality, inexpensive 
mixers for this application having a very high dynamic range (>60dB). Perhaps 
Dan's suggestion of using quadrature sampling is a more cost-effective way to 
implement this, provided red pitaya supports that mode. 

Jishnu 


From: "Hariharan Krishnan"  
To: "casper"  
Sent: Monday, February 10, 2020 4:33:32 PM 
Subject: Re: [casper] Solar Spectrometer Channeliser 

Hi Jishnu, 
Down-conversion is inevitable with red pitaya given the max. sampling frequency 
is 125 MSPS for the on-board ADC (for the 20 - 80 MHz RF band here). The 
dynamic range of the mixer used in the down-conversion becomes rather important 
here primarily because of the RFI channels (AM transmission below 25 MHz) that 
will introduce IMD products. Otherwise I wouldn't expect the dynamic range for 
a relatively clean band to go down at single-stage down-conversion. 

Regards, 
Hari 

On Mon, Feb 10, 2020 at 1:00 AM Jishnu Nambissan T < [ mailto:jis...@rri.res.in 
| jis...@rri.res.in ] > wrote: 



Hi Mugundhan, 

With red pitaya, can you sample 20-80 MHz without downconversion ? And if 
analog down conversion is required, wouldn't that restrict the usable dynamic 
range (unless a high level mixer is used) ? 

Jishnu 


From: "Mugundhan vijayaraghavan" < [ mailto:v.vaishnav151...@gmail.com | 
v.vaishnav151...@gmail.com ] > 
To: "casper" < [ mailto:casper@lists.berkeley.edu | casper@lists.berkeley.edu ] 
> 
Sent: Thursday, February 6, 2020 1:06:09 AM 
Subject: Re: [casper] Solar Spectrometer Channeliser 

Hi Dan, 

We have done integration times from 20ms upto a second. There are bursts that 
last for hours, minutes and a few ms to seconds as well. 

We have not tried AGC on these bursts since we were aiming to study them only. 
In the 8 bit design, we had 3 bits for background and remaining 5 to 
accommodate bursts. 

The red pitaya can still be used if Colm can restrict the band to 20-80 mhz, 
because the ionosphere starts cutting of anything below 20mhz mostly(depending 
on the location of course). Then this can be down converted to fit into 0-62.5 
mhz base band of the red pitaya. 

Thanks, 

Mugundhan 




On Wed, 5 Feb 2020, 22:23 Dan Werthimer, < [ mailto:d...@ssl.berkeley.edu | 
d...@ssl.berkeley.edu ] > wrote: 

BQ_BEGIN


hi mugundhan, 

what's the time scale for these bursts? 
rise and fall times? 
can you use a AGC circuit (automatic gain control), 
eg: computer controlled attenuator 
to turn down the power going into the ADC during the bursts, 
so you could keep the levels going into the ADC relatively constant? 
if the rise and fall times are longer than 1ms (the integration time of the 
spectrometer), 
then you could adjust the power level for each spectrum, and write down where 
you set the attenuator for that spectrum, so you could still know the absolute 
power. 

if not, there are some 14 bit 200 Msps ADC boards, and i think the new RFSOC 
boards/chips have 14 bit ADC's, 
but you'll have to write a casper yellow interface block for this ADC, 
as we don't have a 14 bit 200 Msps ADC in the casper library. 

another possiblity is to multiplex your 80 MHz band, 40 MHz at a time into a 
red pitaya board, 
ping ponging back and forth between bands: 0 to 40 MHz for 1 ms, then 40 to 80 
MHz for the next ms. 

best wishes, 

dan 




On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan < [ 
mailto:v.vaishnav151...@gmail.com | v.vaishnav151...@gmail.com ] > wrote: 

BQ_BEGIN

Hi Dan, 

Usually quiet sun doesn't show such abrupt changes, but bursts do (easily 
40-50dB or more) for bright bursts. We have built 8 bit spectrometers in 
40-80Mhz, but have found then when the burst is pretty strong, saturation 
effects starts kicking in. 


Thanks, 
Mugundhan 


On Wed, 5 Feb 2020, 21:52 Dan Werthimer, < [ mailto:d...@ssl.berkeley.edu | 
d...@ssl.berkeley.edu ] > wrote: 

BQ_BEGIN


hi colm, 
regarding dynamic range 
- 
for your solar spectrometer, do you need 14 bits of ADC dynamic range? 
it's very unusual in radio astronomy to need that much instantaneous dynamic 
range on the input. 
does the sun vary on short time scales in the radio band by factor of 1000 in 
voltage (1,000,000 in power) ? 
or do you have very strong bursting RFI that is 1000 times the average noise 
voltage (1M in power) in the whole band? 

as you probably know, you'll have lots more dynamic range in the output power 
spectrum than the dynamic range of the ADC: 
if you are building a 1024 channel spectrometer with 1 ms integration, 
you'll get about 8 bits more bits of dynamic range above your ADC dynamic range 
in frequency domain voltage, 
which is 16 bits more of dynamic range above your ADC dynamic range in power 
spectra. 
so you'll have about 20 bits of spectral dynamic range if 

Re: [casper] Solar Spectrometer Channeliser

[Dan Werthimer]

if you only want one input, and you can't build a downconverter that
provides the dynamic range,
you might want to consider using the two adc's on the board, and
implementing a quadrature downconverter,
(mix by both 0 and 90 degree LO's and then low pass filter both the
in-phase and quadrature signals),
and then sample a 125 MHz band from -62.5 to +62.5 MHz.

you might also be able interleave the two ADC's to get an effective sample
rate of 250 Msps,
but i don't know if the board will allow you to sample at 0 and 180
degrees,
and it's hard to get the phase, amplitudes and offset matched to minimize
image rejection,
and the adc's might not have enough analog bandwidth.

quadrature dowconverters also need good amplitude and phase matching to
reduce image rejection,
but it's a bit easier to manage this than interleaved adcs.

dan








Dan Werthimer
Marilyn and Watson Alberts Chair
Astronomy Dept and Space Sciences Lab
University of California, Berkeley


On Mon, Feb 10, 2020 at 7:26 AM Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> wrote:

> Hi Ross,
>
> Just to add, we can also have the lo at 80mhz, and use the lower side
> band. 80 will be at 0, 20 will be at 60. But the band can be flipped
> offline.  We can have a strong lpf at 60mhz, which can  cut the lo off
> before downstream processing.
>
> Mugundhan
>
> On Mon, 10 Feb 2020, 15:18 Mugundhan vijayaraghavan, <
> v.vaishnav151...@gmail.com> wrote:
>
>> Hi Ross,
>>
>> I'm not working with Colm on this. So I don't know about the resources
>> available to him.
>>
>> What you're saying is true. Doing it with a single stage may be
>> problematic as with 20 MHz LO, the there will be overlap of the side bands.
>> So, minimally, we need to have two stages. where the 20-80 MHz can be
>> up-converted to outside the band and then down-converted into the base band
>> of 0-60 MHz.
>>
>> Sorry for not being clear earlier.
>>
>> But anyway, for the RedPitaya, due to the sampling restrictions, 20-80
>> MHz band has to be got into 0-60 MHz for getting the full band with the
>> board.
>>
>> Thank you,
>>
>> Mugundhan
>>
>> On Mon, Feb 10, 2020 at 2:32 PM Ross Martin  wrote:
>>
>>> Hi Mugundhan,
>>>
>>> Could you say a little more about how you're downconverting 20-80MHz to
>>> 0-60MHz?  My understanding is that this is not easy to do while retaining
>>> signal quality.  The band overlap of the input and output bands means
>>> simple conversion methods with normal mixers don't work.
>>>
>>> Ross
>>>
>>>
>>> On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
>>> v.vaishnav151...@gmail.com> wrote:
>>>
>>>> Hi jishnu,
>>>>
>>>> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to
>>>> use the band fully. As such, it has a cutoff at 65MHz.
>>>>
>>>> Thanks,
>>>> Mugundhan
>>>>
>>>> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T, 
>>>> wrote:
>>>>
>>>>> Hi Mugundhan,
>>>>>
>>>>> With red pitaya, can you sample 20-80 MHz without downconversion ? And
>>>>> if analog down conversion is required, wouldn't that restrict the usable
>>>>> dynamic range (unless a high level mixer is used) ?
>>>>>
>>>>> Jishnu
>>>>>
>>>>> --
>>>>> *From: *"Mugundhan vijayaraghavan" 
>>>>> *To: *"casper" 
>>>>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>>>>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>>>>
>>>>> Hi Dan,
>>>>>
>>>>> We have done integration times from 20ms upto a second. There are
>>>>> bursts that last for hours, minutes and a few ms to seconds as well.
>>>>>
>>>>> We have not tried AGC on these bursts since we were aiming to study
>>>>> them only. In the 8 bit design, we had 3 bits for background and remaining
>>>>> 5 to accommodate bursts.
>>>>>
>>>>> The red pitaya can still be used if Colm can restrict the band to
>>>>> 20-80 mhz, because the ionosphere starts cutting of anything below 20mhz
>>>>> mostly(depending on the location of course). Then this can be down
>>>>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Mugundhan
>>>

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Hi Ross,

Just to add, we can also have the lo at 80mhz, and use the lower side band.
80 will be at 0, 20 will be at 60. But the band can be flipped offline.  We
can have a strong lpf at 60mhz, which can  cut the lo off before downstream
processing.

Mugundhan

On Mon, 10 Feb 2020, 15:18 Mugundhan vijayaraghavan, <
v.vaishnav151...@gmail.com> wrote:

> Hi Ross,
>
> I'm not working with Colm on this. So I don't know about the resources
> available to him.
>
> What you're saying is true. Doing it with a single stage may be
> problematic as with 20 MHz LO, the there will be overlap of the side bands.
> So, minimally, we need to have two stages. where the 20-80 MHz can be
> up-converted to outside the band and then down-converted into the base band
> of 0-60 MHz.
>
> Sorry for not being clear earlier.
>
> But anyway, for the RedPitaya, due to the sampling restrictions, 20-80 MHz
> band has to be got into 0-60 MHz for getting the full band with the board.
>
> Thank you,
>
> Mugundhan
>
> On Mon, Feb 10, 2020 at 2:32 PM Ross Martin  wrote:
>
>> Hi Mugundhan,
>>
>> Could you say a little more about how you're downconverting 20-80MHz to
>> 0-60MHz?  My understanding is that this is not easy to do while retaining
>> signal quality.  The band overlap of the input and output bands means
>> simple conversion methods with normal mixers don't work.
>>
>> Ross
>>
>>
>> On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
>> v.vaishnav151...@gmail.com> wrote:
>>
>>> Hi jishnu,
>>>
>>> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to use
>>> the band fully. As such, it has a cutoff at 65MHz.
>>>
>>> Thanks,
>>> Mugundhan
>>>
>>> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T, 
>>> wrote:
>>>
>>>> Hi Mugundhan,
>>>>
>>>> With red pitaya, can you sample 20-80 MHz without downconversion ? And
>>>> if analog down conversion is required, wouldn't that restrict the usable
>>>> dynamic range (unless a high level mixer is used) ?
>>>>
>>>> Jishnu
>>>>
>>>> --
>>>> *From: *"Mugundhan vijayaraghavan" 
>>>> *To: *"casper" 
>>>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>>>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>>>
>>>> Hi Dan,
>>>>
>>>> We have done integration times from 20ms upto a second. There are
>>>> bursts that last for hours, minutes and a few ms to seconds as well.
>>>>
>>>> We have not tried AGC on these bursts since we were aiming to study
>>>> them only. In the 8 bit design, we had 3 bits for background and remaining
>>>> 5 to accommodate bursts.
>>>>
>>>> The red pitaya can still be used if Colm can restrict the band to 20-80
>>>> mhz, because the ionosphere starts cutting of anything below 20mhz
>>>> mostly(depending on the location of course). Then this can be down
>>>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>>>
>>>> Thanks,
>>>>
>>>> Mugundhan
>>>>
>>>>
>>>>
>>>>
>>>> On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:
>>>>
>>>>>
>>>>> hi mugundhan,
>>>>>
>>>>> what's the time scale for these bursts?
>>>>> rise and fall times?
>>>>> can you use a AGC circuit (automatic gain control),
>>>>> eg: computer controlled attenuator
>>>>> to turn down the power going into the ADC during the bursts,
>>>>> so you could keep the levels going into the ADC relatively constant?
>>>>> if the rise and fall times are longer than 1ms (the integration time
>>>>> of the spectrometer),
>>>>> then you could adjust the power level for each spectrum, and write
>>>>> down where
>>>>> you set the attenuator for that spectrum, so you could still know the
>>>>> absolute power.
>>>>>
>>>>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the
>>>>> new RFSOC boards/chips have 14 bit ADC's,
>>>>> but you'll have to write a casper yellow interface block for this
>>>>> ADC,
>>>>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>>>>
>>>>> another possiblity is to multiplex your 80 M

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Hi Ross,

I'm not working with Colm on this. So I don't know about the resources
available to him.

What you're saying is true. Doing it with a single stage may be problematic
as with 20 MHz LO, the there will be overlap of the side bands. So,
minimally, we need to have two stages. where the 20-80 MHz can be
up-converted to outside the band and then down-converted into the base band
of 0-60 MHz.

Sorry for not being clear earlier.

But anyway, for the RedPitaya, due to the sampling restrictions, 20-80 MHz
band has to be got into 0-60 MHz for getting the full band with the board.

Thank you,

Mugundhan

On Mon, Feb 10, 2020 at 2:32 PM Ross Martin  wrote:

> Hi Mugundhan,
>
> Could you say a little more about how you're downconverting 20-80MHz to
> 0-60MHz?  My understanding is that this is not easy to do while retaining
> signal quality.  The band overlap of the input and output bands means
> simple conversion methods with normal mixers don't work.
>
> Ross
>
>
> On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
> v.vaishnav151...@gmail.com> wrote:
>
>> Hi jishnu,
>>
>> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to use
>> the band fully. As such, it has a cutoff at 65MHz.
>>
>> Thanks,
>> Mugundhan
>>
>> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T,  wrote:
>>
>>> Hi Mugundhan,
>>>
>>> With red pitaya, can you sample 20-80 MHz without downconversion ? And
>>> if analog down conversion is required, wouldn't that restrict the usable
>>> dynamic range (unless a high level mixer is used) ?
>>>
>>> Jishnu
>>>
>>> ------
>>> *From: *"Mugundhan vijayaraghavan" 
>>> *To: *"casper" 
>>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>>
>>> Hi Dan,
>>>
>>> We have done integration times from 20ms upto a second. There are bursts
>>> that last for hours, minutes and a few ms to seconds as well.
>>>
>>> We have not tried AGC on these bursts since we were aiming to study them
>>> only. In the 8 bit design, we had 3 bits for background and remaining 5 to
>>> accommodate bursts.
>>>
>>> The red pitaya can still be used if Colm can restrict the band to 20-80
>>> mhz, because the ionosphere starts cutting of anything below 20mhz
>>> mostly(depending on the location of course). Then this can be down
>>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>>
>>> Thanks,
>>>
>>> Mugundhan
>>>
>>>
>>>
>>>
>>> On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:
>>>
>>>>
>>>> hi mugundhan,
>>>>
>>>> what's the time scale for these bursts?
>>>> rise and fall times?
>>>> can you use a AGC circuit (automatic gain control),
>>>> eg: computer controlled attenuator
>>>> to turn down the power going into the ADC during the bursts,
>>>> so you could keep the levels going into the ADC relatively constant?
>>>> if the rise and fall times are longer than 1ms (the integration time of
>>>> the spectrometer),
>>>> then you could adjust the power level for each spectrum, and write down
>>>> where
>>>> you set the attenuator for that spectrum, so you could still know the
>>>> absolute power.
>>>>
>>>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
>>>> RFSOC boards/chips have 14 bit ADC's,
>>>> but you'll have to write a casper yellow interface block for this ADC,
>>>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>>>
>>>> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time
>>>> into a red pitaya board,
>>>> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then
>>>> 40 to 80 MHz for the next ms.
>>>>
>>>>
>>>> best wishes,
>>>>
>>>> dan
>>>>
>>>>
>>>>
>>>>
>>>> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
>>>> v.vaishnav151...@gmail.com> wrote:
>>>>
>>>>> Hi Dan,
>>>>>
>>>>> Usually quiet sun doesn't show such abrupt changes, but bursts do
>>>>> (easily 40-50dB or more) for bright bursts. We have built 8 bit
>>>>> spectrometers in 40-80Mhz, but have found then when the bur

Re: [casper] Solar Spectrometer Channeliser

[Ross Martin]

Hi Mugundhan,

Could you say a little more about how you're downconverting 20-80MHz to
0-60MHz?  My understanding is that this is not easy to do while retaining
signal quality.  The band overlap of the input and output bands means
simple conversion methods with normal mixers don't work.

Ross


On Mon, Feb 10, 2020, 1:09 AM Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> wrote:

> Hi jishnu,
>
> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to use
> the band fully. As such, it has a cutoff at 65MHz.
>
> Thanks,
> Mugundhan
>
> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T,  wrote:
>
>> Hi Mugundhan,
>>
>> With red pitaya, can you sample 20-80 MHz without downconversion ? And if
>> analog down conversion is required, wouldn't that restrict the usable
>> dynamic range (unless a high level mixer is used) ?
>>
>> Jishnu
>>
>> --
>> *From: *"Mugundhan vijayaraghavan" 
>> *To: *"casper" 
>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>
>> Hi Dan,
>>
>> We have done integration times from 20ms upto a second. There are bursts
>> that last for hours, minutes and a few ms to seconds as well.
>>
>> We have not tried AGC on these bursts since we were aiming to study them
>> only. In the 8 bit design, we had 3 bits for background and remaining 5 to
>> accommodate bursts.
>>
>> The red pitaya can still be used if Colm can restrict the band to 20-80
>> mhz, because the ionosphere starts cutting of anything below 20mhz
>> mostly(depending on the location of course). Then this can be down
>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>
>> Thanks,
>>
>> Mugundhan
>>
>>
>>
>>
>> On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:
>>
>>>
>>> hi mugundhan,
>>>
>>> what's the time scale for these bursts?
>>> rise and fall times?
>>> can you use a AGC circuit (automatic gain control),
>>> eg: computer controlled attenuator
>>> to turn down the power going into the ADC during the bursts,
>>> so you could keep the levels going into the ADC relatively constant?
>>> if the rise and fall times are longer than 1ms (the integration time of
>>> the spectrometer),
>>> then you could adjust the power level for each spectrum, and write down
>>> where
>>> you set the attenuator for that spectrum, so you could still know the
>>> absolute power.
>>>
>>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
>>> RFSOC boards/chips have 14 bit ADC's,
>>> but you'll have to write a casper yellow interface block for this ADC,
>>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>>
>>> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time
>>> into a red pitaya board,
>>> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then
>>> 40 to 80 MHz for the next ms.
>>>
>>>
>>> best wishes,
>>>
>>> dan
>>>
>>>
>>>
>>>
>>> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
>>> v.vaishnav151...@gmail.com> wrote:
>>>
>>>> Hi Dan,
>>>>
>>>> Usually quiet sun doesn't show such abrupt changes, but bursts do
>>>> (easily 40-50dB or more) for bright bursts. We have built 8 bit
>>>> spectrometers in 40-80Mhz, but have found then when the burst is pretty
>>>> strong, saturation effects starts kicking in.
>>>>
>>>>
>>>> Thanks,
>>>> Mugundhan
>>>>
>>>>
>>>> On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:
>>>>
>>>>>
>>>>> hi colm,
>>>>> regarding dynamic range
>>>>> -
>>>>> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
>>>>> it's very unusual in radio astronomy to need that much instantaneous
>>>>> dynamic range on the input.
>>>>> does the sun vary on short time scales in the radio band by factor of
>>>>> 1000 in voltage (1,000,000 in power) ?
>>>>> or do you have very strong bursting RFI that is 1000 times the average
>>>>> noise voltage (1M in power) in the whole band?
>>>>>
>>>>> as you probably know, you'll have lots more dynamic range in the
&

Re: [casper] Solar Spectrometer Channeliser

[Hariharan Krishnan]

Hi Jishnu,
 Down-conversion is inevitable with red pitaya given the max.
sampling frequency is 125 MSPS for the on-board ADC (for the 20 - 80 MHz RF
band here).  The dynamic range of the mixer used in the down-conversion
becomes rather important here primarily because of the RFI channels (AM
transmission below 25 MHz) that will introduce IMD products. Otherwise I
wouldn't expect the dynamic range for a relatively clean band to go down at
single-stage down-conversion.

Regards,
Hari

On Mon, Feb 10, 2020 at 1:00 AM Jishnu Nambissan T 
wrote:

> Hi Mugundhan,
>
> With red pitaya, can you sample 20-80 MHz without downconversion ? And if
> analog down conversion is required, wouldn't that restrict the usable
> dynamic range (unless a high level mixer is used) ?
>
> Jishnu
>
> --
> *From: *"Mugundhan vijayaraghavan" 
> *To: *"casper" 
> *Sent: *Thursday, February 6, 2020 1:06:09 AM
> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>
> Hi Dan,
>
> We have done integration times from 20ms upto a second. There are bursts
> that last for hours, minutes and a few ms to seconds as well.
>
> We have not tried AGC on these bursts since we were aiming to study them
> only. In the 8 bit design, we had 3 bits for background and remaining 5 to
> accommodate bursts.
>
> The red pitaya can still be used if Colm can restrict the band to 20-80
> mhz, because the ionosphere starts cutting of anything below 20mhz
> mostly(depending on the location of course). Then this can be down
> converted to fit into 0-62.5 mhz base band of the red pitaya.
>
> Thanks,
>
> Mugundhan
>
>
>
>
> On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:
>
>>
>> hi mugundhan,
>>
>> what's the time scale for these bursts?
>> rise and fall times?
>> can you use a AGC circuit (automatic gain control),
>> eg: computer controlled attenuator
>> to turn down the power going into the ADC during the bursts,
>> so you could keep the levels going into the ADC relatively constant?
>> if the rise and fall times are longer than 1ms (the integration time of
>> the spectrometer),
>> then you could adjust the power level for each spectrum, and write down
>> where
>> you set the attenuator for that spectrum, so you could still know the
>> absolute power.
>>
>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
>> RFSOC boards/chips have 14 bit ADC's,
>> but you'll have to write a casper yellow interface block for this ADC,
>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>
>> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time
>> into a red pitaya board,
>> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then 40
>> to 80 MHz for the next ms.
>>
>>
>> best wishes,
>>
>> dan
>>
>>
>>
>>
>> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
>> v.vaishnav151...@gmail.com> wrote:
>>
>>> Hi Dan,
>>>
>>> Usually quiet sun doesn't show such abrupt changes, but bursts do
>>> (easily 40-50dB or more) for bright bursts. We have built 8 bit
>>> spectrometers in 40-80Mhz, but have found then when the burst is pretty
>>> strong, saturation effects starts kicking in.
>>>
>>>
>>> Thanks,
>>> Mugundhan
>>>
>>>
>>> On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:
>>>
>>>>
>>>> hi colm,
>>>> regarding dynamic range
>>>> -
>>>> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
>>>> it's very unusual in radio astronomy to need that much instantaneous
>>>> dynamic range on the input.
>>>> does the sun vary on short time scales in the radio band by factor of
>>>> 1000 in voltage (1,000,000 in power) ?
>>>> or do you have very strong bursting RFI that is 1000 times the average
>>>> noise voltage (1M in power) in the whole band?
>>>>
>>>> as you probably know, you'll have lots more dynamic range in the output
>>>> power spectrum than the dynamic range of the ADC:
>>>> if you are building a 1024 channel spectrometer with 1 ms integration,
>>>> you'll get about 8 bits more bits of dynamic range above your ADC
>>>> dynamic range in frequency domain voltage,
>>>> which is 16 bits more of dynamic range above your ADC dynamic range in
>>>> power spectra.
>>>> so you'll have about 20 bits of spectral dynamic range if yo

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Sorry Jishnu, I didn't see the mixer question.

If the mixer has a poorer dynamic range than the ADC, then the chain's DR
is limited by that. So, as far as the mixer's DR is better than a 14 bit
ADCs, it should be fine.

Mugundhan

On Mon, Feb 10, 2020 at 1:38 PM Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> wrote:

> Hi jishnu,
>
> With red pitaya,  you have to down convert 20-80 to 0-60 baseband to use
> the band fully. As such, it has a cutoff at 65MHz.
>
> Thanks,
> Mugundhan
>
> On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T,  wrote:
>
>> Hi Mugundhan,
>>
>> With red pitaya, can you sample 20-80 MHz without downconversion ? And if
>> analog down conversion is required, wouldn't that restrict the usable
>> dynamic range (unless a high level mixer is used) ?
>>
>> Jishnu
>>
>> --
>> *From: *"Mugundhan vijayaraghavan" 
>> *To: *"casper" 
>> *Sent: *Thursday, February 6, 2020 1:06:09 AM
>> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>>
>> Hi Dan,
>>
>> We have done integration times from 20ms upto a second. There are bursts
>> that last for hours, minutes and a few ms to seconds as well.
>>
>> We have not tried AGC on these bursts since we were aiming to study them
>> only. In the 8 bit design, we had 3 bits for background and remaining 5 to
>> accommodate bursts.
>>
>> The red pitaya can still be used if Colm can restrict the band to 20-80
>> mhz, because the ionosphere starts cutting of anything below 20mhz
>> mostly(depending on the location of course). Then this can be down
>> converted to fit into 0-62.5 mhz base band of the red pitaya.
>>
>> Thanks,
>>
>> Mugundhan
>>
>>
>>
>>
>> On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:
>>
>>>
>>> hi mugundhan,
>>>
>>> what's the time scale for these bursts?
>>> rise and fall times?
>>> can you use a AGC circuit (automatic gain control),
>>> eg: computer controlled attenuator
>>> to turn down the power going into the ADC during the bursts,
>>> so you could keep the levels going into the ADC relatively constant?
>>> if the rise and fall times are longer than 1ms (the integration time of
>>> the spectrometer),
>>> then you could adjust the power level for each spectrum, and write down
>>> where
>>> you set the attenuator for that spectrum, so you could still know the
>>> absolute power.
>>>
>>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
>>> RFSOC boards/chips have 14 bit ADC's,
>>> but you'll have to write a casper yellow interface block for this ADC,
>>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>>
>>> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time
>>> into a red pitaya board,
>>> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then
>>> 40 to 80 MHz for the next ms.
>>>
>>>
>>> best wishes,
>>>
>>> dan
>>>
>>>
>>>
>>>
>>> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
>>> v.vaishnav151...@gmail.com> wrote:
>>>
>>>> Hi Dan,
>>>>
>>>> Usually quiet sun doesn't show such abrupt changes, but bursts do
>>>> (easily 40-50dB or more) for bright bursts. We have built 8 bit
>>>> spectrometers in 40-80Mhz, but have found then when the burst is pretty
>>>> strong, saturation effects starts kicking in.
>>>>
>>>>
>>>> Thanks,
>>>> Mugundhan
>>>>
>>>>
>>>> On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:
>>>>
>>>>>
>>>>> hi colm,
>>>>> regarding dynamic range
>>>>> -
>>>>> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
>>>>> it's very unusual in radio astronomy to need that much instantaneous
>>>>> dynamic range on the input.
>>>>> does the sun vary on short time scales in the radio band by factor of
>>>>> 1000 in voltage (1,000,000 in power) ?
>>>>> or do you have very strong bursting RFI that is 1000 times the average
>>>>> noise voltage (1M in power) in the whole band?
>>>>>
>>>>> as you probably know, you'll have lots more dynamic range in the
>>>>> output power spectrum than the dynamic ran

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Hi jishnu,

With red pitaya,  you have to down convert 20-80 to 0-60 baseband to use
the band fully. As such, it has a cutoff at 65MHz.

Thanks,
Mugundhan

On Mon, 10 Feb 2020, 13:30 Jishnu Nambissan T,  wrote:

> Hi Mugundhan,
>
> With red pitaya, can you sample 20-80 MHz without downconversion ? And if
> analog down conversion is required, wouldn't that restrict the usable
> dynamic range (unless a high level mixer is used) ?
>
> Jishnu
>
> --
> *From: *"Mugundhan vijayaraghavan" 
> *To: *"casper" 
> *Sent: *Thursday, February 6, 2020 1:06:09 AM
> *Subject: *Re: [casper] Solar Spectrometer Channeliser
>
> Hi Dan,
>
> We have done integration times from 20ms upto a second. There are bursts
> that last for hours, minutes and a few ms to seconds as well.
>
> We have not tried AGC on these bursts since we were aiming to study them
> only. In the 8 bit design, we had 3 bits for background and remaining 5 to
> accommodate bursts.
>
> The red pitaya can still be used if Colm can restrict the band to 20-80
> mhz, because the ionosphere starts cutting of anything below 20mhz
> mostly(depending on the location of course). Then this can be down
> converted to fit into 0-62.5 mhz base band of the red pitaya.
>
> Thanks,
>
> Mugundhan
>
>
>
>
> On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:
>
>>
>> hi mugundhan,
>>
>> what's the time scale for these bursts?
>> rise and fall times?
>> can you use a AGC circuit (automatic gain control),
>> eg: computer controlled attenuator
>> to turn down the power going into the ADC during the bursts,
>> so you could keep the levels going into the ADC relatively constant?
>> if the rise and fall times are longer than 1ms (the integration time of
>> the spectrometer),
>> then you could adjust the power level for each spectrum, and write down
>> where
>> you set the attenuator for that spectrum, so you could still know the
>> absolute power.
>>
>> if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
>> RFSOC boards/chips have 14 bit ADC's,
>> but you'll have to write a casper yellow interface block for this ADC,
>> as we don't have a 14 bit 200 Msps ADC in the casper library.
>>
>> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time
>> into a red pitaya board,
>> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then 40
>> to 80 MHz for the next ms.
>>
>>
>> best wishes,
>>
>> dan
>>
>>
>>
>>
>> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
>> v.vaishnav151...@gmail.com> wrote:
>>
>>> Hi Dan,
>>>
>>> Usually quiet sun doesn't show such abrupt changes, but bursts do
>>> (easily 40-50dB or more) for bright bursts. We have built 8 bit
>>> spectrometers in 40-80Mhz, but have found then when the burst is pretty
>>> strong, saturation effects starts kicking in.
>>>
>>>
>>> Thanks,
>>> Mugundhan
>>>
>>>
>>> On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:
>>>
>>>>
>>>> hi colm,
>>>> regarding dynamic range
>>>> -
>>>> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
>>>> it's very unusual in radio astronomy to need that much instantaneous
>>>> dynamic range on the input.
>>>> does the sun vary on short time scales in the radio band by factor of
>>>> 1000 in voltage (1,000,000 in power) ?
>>>> or do you have very strong bursting RFI that is 1000 times the average
>>>> noise voltage (1M in power) in the whole band?
>>>>
>>>> as you probably know, you'll have lots more dynamic range in the output
>>>> power spectrum than the dynamic range of the ADC:
>>>> if you are building a 1024 channel spectrometer with 1 ms integration,
>>>> you'll get about 8 bits more bits of dynamic range above your ADC
>>>> dynamic range in frequency domain voltage,
>>>> which is 16 bits more of dynamic range above your ADC dynamic range in
>>>> power spectra.
>>>> so you'll have about 20 bits of spectral dynamic range if you use an 8
>>>> bit ADC,
>>>> (power spectrum dynamic range of about 1 million in 1 ms with an 8 bit
>>>> ADC, setting noise at 3 bit RMS).
>>>> and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12
>>>> bit ADC, and 32 bits for for 14 bit ADC).
>>>>
&g

Re: [casper] Solar Spectrometer Channeliser

[Jishnu Nambissan T]

Hi Mugundhan, 

With red pitaya, can you sample 20-80 MHz without downconversion ? And if 
analog down conversion is required, wouldn't that restrict the usable dynamic 
range (unless a high level mixer is used) ? 

Jishnu 


From: "Mugundhan vijayaraghavan"  
To: "casper"  
Sent: Thursday, February 6, 2020 1:06:09 AM 
Subject: Re: [casper] Solar Spectrometer Channeliser 

Hi Dan, 

We have done integration times from 20ms upto a second. There are bursts that 
last for hours, minutes and a few ms to seconds as well. 

We have not tried AGC on these bursts since we were aiming to study them only. 
In the 8 bit design, we had 3 bits for background and remaining 5 to 
accommodate bursts. 

The red pitaya can still be used if Colm can restrict the band to 20-80 mhz, 
because the ionosphere starts cutting of anything below 20mhz mostly(depending 
on the location of course). Then this can be down converted to fit into 0-62.5 
mhz base band of the red pitaya. 

Thanks, 

Mugundhan 




On Wed, 5 Feb 2020, 22:23 Dan Werthimer, < [ mailto:d...@ssl.berkeley.edu | 
d...@ssl.berkeley.edu ] > wrote: 




hi mugundhan, 

what's the time scale for these bursts? 
rise and fall times? 
can you use a AGC circuit (automatic gain control), 
eg: computer controlled attenuator 
to turn down the power going into the ADC during the bursts, 
so you could keep the levels going into the ADC relatively constant? 
if the rise and fall times are longer than 1ms (the integration time of the 
spectrometer), 
then you could adjust the power level for each spectrum, and write down where 
you set the attenuator for that spectrum, so you could still know the absolute 
power. 

if not, there are some 14 bit 200 Msps ADC boards, and i think the new RFSOC 
boards/chips have 14 bit ADC's, 
but you'll have to write a casper yellow interface block for this ADC, 
as we don't have a 14 bit 200 Msps ADC in the casper library. 

another possiblity is to multiplex your 80 MHz band, 40 MHz at a time into a 
red pitaya board, 
ping ponging back and forth between bands: 0 to 40 MHz for 1 ms, then 40 to 80 
MHz for the next ms. 

best wishes, 

dan 




On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan < [ 
mailto:v.vaishnav151...@gmail.com | v.vaishnav151...@gmail.com ] > wrote: 

BQ_BEGIN

Hi Dan, 

Usually quiet sun doesn't show such abrupt changes, but bursts do (easily 
40-50dB or more) for bright bursts. We have built 8 bit spectrometers in 
40-80Mhz, but have found then when the burst is pretty strong, saturation 
effects starts kicking in. 


Thanks, 
Mugundhan 


On Wed, 5 Feb 2020, 21:52 Dan Werthimer, < [ mailto:d...@ssl.berkeley.edu | 
d...@ssl.berkeley.edu ] > wrote: 

BQ_BEGIN


hi colm, 
regarding dynamic range 
- 
for your solar spectrometer, do you need 14 bits of ADC dynamic range? 
it's very unusual in radio astronomy to need that much instantaneous dynamic 
range on the input. 
does the sun vary on short time scales in the radio band by factor of 1000 in 
voltage (1,000,000 in power) ? 
or do you have very strong bursting RFI that is 1000 times the average noise 
voltage (1M in power) in the whole band? 

as you probably know, you'll have lots more dynamic range in the output power 
spectrum than the dynamic range of the ADC: 
if you are building a 1024 channel spectrometer with 1 ms integration, 
you'll get about 8 bits more bits of dynamic range above your ADC dynamic range 
in frequency domain voltage, 
which is 16 bits more of dynamic range above your ADC dynamic range in power 
spectra. 
so you'll have about 20 bits of spectral dynamic range if you use an 8 bit ADC, 
(power spectrum dynamic range of about 1 million in 1 ms with an 8 bit ADC, 
setting noise at 3 bit RMS). 
and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12 bit 
ADC, and 32 bits for for 14 bit ADC). 

regarding boards for your spectrometer 
--- 

1) as adam pointed out, the red pitaya is cheap, but sample rate and bandwidth 
don't quite get the specs you need. 

2) another possibility is to use a snap board, which costs more, but can sample 
3 inputs at 950 Msps, 
or 6 inputs at 500 Msps, or 12 inputs at 250 Msps with 8 bit ADC's. most people 
populate the snap board with 8 bit ADCs, 
but a few people have populated it with 12 bit ADC's, although the sample rate 
goes down by 8/12. 

3) another possibility is to use a xilinx RFSOC board. the first gen has a bank 
of 12 bit ADC's (8 inputs at 4 Gsps, or 16 inputs at 2 Gsps), 
but i think the new generation has 14 bit ADC's ? the RFSOC boards cost more 
than snaps, but RFSOC was designed 
in dublin, so you can probably get one from xilinx dublin the ZCU111 board 
has not been fully casperized yet though. 

best wishes, 

dan 




Dan Werthimer 
Marilyn and Watson Alberts Chair 
Astronomy Dept and Space Sciences Lab 
University of California, Berkeley 


On We

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Hi Dan,

We have done integration times from 20ms upto a second. There are bursts
that last for hours, minutes and a few ms to seconds as well.

We have not tried AGC on these bursts since we were aiming to study them
only. In the 8 bit design, we had 3 bits for background and remaining 5 to
accommodate bursts.

The red pitaya can still be used if Colm can restrict the band to 20-80
mhz, because the ionosphere starts cutting of anything below 20mhz
mostly(depending on the location of course). Then this can be down
converted to fit into 0-62.5 mhz base band of the red pitaya.

Thanks,

Mugundhan




On Wed, 5 Feb 2020, 22:23 Dan Werthimer,  wrote:

>
> hi mugundhan,
>
> what's the time scale for these bursts?
> rise and fall times?
> can you use a AGC circuit (automatic gain control),
> eg: computer controlled attenuator
> to turn down the power going into the ADC during the bursts,
> so you could keep the levels going into the ADC relatively constant?
> if the rise and fall times are longer than 1ms (the integration time of
> the spectrometer),
> then you could adjust the power level for each spectrum, and write down
> where
> you set the attenuator for that spectrum, so you could still know the
> absolute power.
>
> if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
> RFSOC boards/chips have 14 bit ADC's,
> but you'll have to write a casper yellow interface block for this ADC,
> as we don't have a 14 bit 200 Msps ADC in the casper library.
>
> another possiblity is to multiplex your 80 MHz band, 40 MHz at a time into
> a red pitaya board,
> ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then 40
> to 80 MHz for the next ms.
>
>
> best wishes,
>
> dan
>
>
>
>
> On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
> v.vaishnav151...@gmail.com> wrote:
>
>> Hi Dan,
>>
>> Usually quiet sun doesn't show such abrupt changes, but bursts do (easily
>> 40-50dB or more) for bright bursts. We have built 8 bit spectrometers in
>> 40-80Mhz, but have found then when the burst is pretty strong, saturation
>> effects starts kicking in.
>>
>>
>> Thanks,
>> Mugundhan
>>
>>
>> On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:
>>
>>>
>>> hi colm,
>>>
>>> regarding dynamic range
>>> -
>>> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
>>> it's very unusual in radio astronomy to need that much instantaneous
>>> dynamic range on the input.
>>> does the sun vary on short time scales in the radio band by factor of
>>> 1000 in voltage (1,000,000 in power) ?
>>> or do you have very strong bursting RFI that is 1000 times the average
>>> noise voltage (1M in power) in the whole band?
>>>
>>> as you probably know, you'll have lots more dynamic range in the output
>>> power spectrum than the dynamic range of the ADC:
>>> if you are building a 1024 channel spectrometer with 1 ms integration,
>>> you'll get about 8 bits more bits of dynamic range above your ADC
>>> dynamic range in frequency domain voltage,
>>> which is 16 bits more of dynamic range above your ADC dynamic range in
>>> power spectra.
>>> so you'll have about 20 bits of spectral dynamic range if you use an 8
>>> bit ADC,
>>> (power spectrum dynamic range of about 1 million in 1 ms with an 8 bit
>>> ADC, setting noise at 3 bit RMS).
>>> and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12
>>> bit ADC, and 32 bits for for 14 bit ADC).
>>>
>>> regarding boards for your spectrometer
>>> ---
>>>
>>> 1) as adam pointed out, the red pitaya is cheap, but sample rate and
>>> bandwidth don't quite get the specs you need.
>>>
>>> 2)  another possibility is to use a snap board, which costs more, but
>>> can sample 3 inputs at 950 Msps,
>>> or 6 inputs at 500 Msps, or 12 inputs at 250 Msps with 8 bit ADC's.
>>> most people populate the snap board with 8 bit ADCs,
>>> but a few people have populated it with 12 bit ADC's, although the
>>> sample rate goes down by 8/12.
>>>
>>> 3) another possibility is to use a xilinx RFSOC board.  the first gen
>>> has a bank of 12 bit ADC's  (8 inputs at 4 Gsps, or 16 inputs at 2 Gsps),
>>> but i think the new generation has 14 bit ADC's ?the RFSOC boards
>>> cost more than snaps, but RFSOC was designed
>>> in dublin, so you can probably get one from xilinx dublin   the
>>> ZCU111 board has not been fully casperized yet though.
>>>
>>> best wishes,
>>>
>>> dan
>>>
>>>
>>>
>>>
>>>
>>> Dan Werthimer
>>> Marilyn and Watson Alberts Chair
>>> Astronomy Dept and Space Sciences Lab
>>> University of California, Berkeley
>>>
>>>
>>> On Wed, Feb 5, 2020 at 5:06 AM Colm Bracken 
>>> wrote:
>>>
 Hello CASPER people,

 We are looking to build a spectrometer with not too demanding
 requirements.
 Based on the specs below, would the Red Pitaya be up to the job do you
 think?
 Or, is there another, better suited (but similarly affordable) solution?

 Chanel 

Re: [casper] Solar Spectrometer Channeliser

[Dan Werthimer]

hi mugundhan,

what's the time scale for these bursts?
rise and fall times?
can you use a AGC circuit (automatic gain control),
eg: computer controlled attenuator
to turn down the power going into the ADC during the bursts,
so you could keep the levels going into the ADC relatively constant?
if the rise and fall times are longer than 1ms (the integration time of the
spectrometer),
then you could adjust the power level for each spectrum, and write down
where
you set the attenuator for that spectrum, so you could still know the
absolute power.

if not, there are some 14 bit 200 Msps ADC boards,  and i think the new
RFSOC boards/chips have 14 bit ADC's,
but you'll have to write a casper yellow interface block for this ADC,
as we don't have a 14 bit 200 Msps ADC in the casper library.

another possiblity is to multiplex your 80 MHz band, 40 MHz at a time into
a red pitaya board,
ping ponging back and forth between bands:  0 to 40 MHz for 1 ms, then 40
to 80 MHz for the next ms.


best wishes,

dan




On Wed, Feb 5, 2020 at 8:33 AM Mugundhan vijayaraghavan <
v.vaishnav151...@gmail.com> wrote:

> Hi Dan,
>
> Usually quiet sun doesn't show such abrupt changes, but bursts do (easily
> 40-50dB or more) for bright bursts. We have built 8 bit spectrometers in
> 40-80Mhz, but have found then when the burst is pretty strong, saturation
> effects starts kicking in.
>
>
> Thanks,
> Mugundhan
>
>
> On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:
>
>>
>> hi colm,
>>
>> regarding dynamic range
>> -
>> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
>> it's very unusual in radio astronomy to need that much instantaneous
>> dynamic range on the input.
>> does the sun vary on short time scales in the radio band by factor of
>> 1000 in voltage (1,000,000 in power) ?
>> or do you have very strong bursting RFI that is 1000 times the average
>> noise voltage (1M in power) in the whole band?
>>
>> as you probably know, you'll have lots more dynamic range in the output
>> power spectrum than the dynamic range of the ADC:
>> if you are building a 1024 channel spectrometer with 1 ms integration,
>> you'll get about 8 bits more bits of dynamic range above your ADC dynamic
>> range in frequency domain voltage,
>> which is 16 bits more of dynamic range above your ADC dynamic range in
>> power spectra.
>> so you'll have about 20 bits of spectral dynamic range if you use an 8
>> bit ADC,
>> (power spectrum dynamic range of about 1 million in 1 ms with an 8 bit
>> ADC, setting noise at 3 bit RMS).
>> and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12
>> bit ADC, and 32 bits for for 14 bit ADC).
>>
>> regarding boards for your spectrometer
>> ---
>>
>> 1) as adam pointed out, the red pitaya is cheap, but sample rate and
>> bandwidth don't quite get the specs you need.
>>
>> 2)  another possibility is to use a snap board, which costs more, but can
>> sample 3 inputs at 950 Msps,
>> or 6 inputs at 500 Msps, or 12 inputs at 250 Msps with 8 bit ADC's.  most
>> people populate the snap board with 8 bit ADCs,
>> but a few people have populated it with 12 bit ADC's, although the sample
>> rate goes down by 8/12.
>>
>> 3) another possibility is to use a xilinx RFSOC board.  the first gen has
>> a bank of 12 bit ADC's  (8 inputs at 4 Gsps, or 16 inputs at 2 Gsps),
>> but i think the new generation has 14 bit ADC's ?the RFSOC boards
>> cost more than snaps, but RFSOC was designed
>> in dublin, so you can probably get one from xilinx dublin   the
>> ZCU111 board has not been fully casperized yet though.
>>
>> best wishes,
>>
>> dan
>>
>>
>>
>>
>>
>> Dan Werthimer
>> Marilyn and Watson Alberts Chair
>> Astronomy Dept and Space Sciences Lab
>> University of California, Berkeley
>>
>>
>> On Wed, Feb 5, 2020 at 5:06 AM Colm Bracken 
>> wrote:
>>
>>> Hello CASPER people,
>>>
>>> We are looking to build a spectrometer with not too demanding
>>> requirements.
>>> Based on the specs below, would the Red Pitaya be up to the job do you
>>> think?
>>> Or, is there another, better suited (but similarly affordable) solution?
>>>
>>> Chanel widths: ~< 100 kHz
>>> Time sampling: ~< millisecond
>>> Polarisation: 2 channels
>>> Antenna freq range: 10-85 MHz (total bandwidth of 75 MHz)
>>> Digitisation: 14 bit
>>>
>>> Any advice on this would be great!
>>>
>>> Thanks in advance,
>>> Colm
>>> --
>>>
>>> *Dr Colm Bracken*
>>> Lecturer
>>> Maynooth University Experimental Physics
>>>
>>>
>>> Maynooth University, Maynooth, Co. Kildare, Ireland.
>>>
>>> T: +353 1 708 3641
>>> E: colm.brac...@mu.ie W: www.maynoothuniversity.ie
>>>
>>> Follow my work on https://nuim.academia.edu/ColmBracken
>>>
>>>
>>>
>>> And
>>>
>>>
>>> Research Associate
>>>
>>> Astronomy & Astrophysics Section
>>> School of Cosmic Physics
>>> Dublin Institute for Advanced Studies
>>> 31 Fitzwilliam Place
>>> Dublin 2, D02 XF86
>>>
>>>
>>>
>>> T: +353 1 440 6656 ext 352
>>> 

Re: [casper] Solar Spectrometer Channeliser

[Mugundhan vijayaraghavan]

Hi Dan,

Usually quiet sun doesn't show such abrupt changes, but bursts do (easily
40-50dB or more) for bright bursts. We have built 8 bit spectrometers in
40-80Mhz, but have found then when the burst is pretty strong, saturation
effects starts kicking in.


Thanks,
Mugundhan


On Wed, 5 Feb 2020, 21:52 Dan Werthimer,  wrote:

>
> hi colm,
>
> regarding dynamic range
> -
> for your solar spectrometer, do you need 14 bits of ADC dynamic range?
> it's very unusual in radio astronomy to need that much instantaneous
> dynamic range on the input.
> does the sun vary on short time scales in the radio band by factor of 1000
> in voltage (1,000,000 in power) ?
> or do you have very strong bursting RFI that is 1000 times the average
> noise voltage (1M in power) in the whole band?
>
> as you probably know, you'll have lots more dynamic range in the output
> power spectrum than the dynamic range of the ADC:
> if you are building a 1024 channel spectrometer with 1 ms integration,
> you'll get about 8 bits more bits of dynamic range above your ADC dynamic
> range in frequency domain voltage,
> which is 16 bits more of dynamic range above your ADC dynamic range in
> power spectra.
> so you'll have about 20 bits of spectral dynamic range if you use an 8 bit
> ADC,
> (power spectrum dynamic range of about 1 million in 1 ms with an 8 bit
> ADC, setting noise at 3 bit RMS).
> and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12
> bit ADC, and 32 bits for for 14 bit ADC).
>
> regarding boards for your spectrometer
> ---
>
> 1) as adam pointed out, the red pitaya is cheap, but sample rate and
> bandwidth don't quite get the specs you need.
>
> 2)  another possibility is to use a snap board, which costs more, but can
> sample 3 inputs at 950 Msps,
> or 6 inputs at 500 Msps, or 12 inputs at 250 Msps with 8 bit ADC's.  most
> people populate the snap board with 8 bit ADCs,
> but a few people have populated it with 12 bit ADC's, although the sample
> rate goes down by 8/12.
>
> 3) another possibility is to use a xilinx RFSOC board.  the first gen has
> a bank of 12 bit ADC's  (8 inputs at 4 Gsps, or 16 inputs at 2 Gsps),
> but i think the new generation has 14 bit ADC's ?the RFSOC boards cost
> more than snaps, but RFSOC was designed
> in dublin, so you can probably get one from xilinx dublin   the ZCU111
> board has not been fully casperized yet though.
>
> best wishes,
>
> dan
>
>
>
>
>
> Dan Werthimer
> Marilyn and Watson Alberts Chair
> Astronomy Dept and Space Sciences Lab
> University of California, Berkeley
>
>
> On Wed, Feb 5, 2020 at 5:06 AM Colm Bracken  wrote:
>
>> Hello CASPER people,
>>
>> We are looking to build a spectrometer with not too demanding
>> requirements.
>> Based on the specs below, would the Red Pitaya be up to the job do you
>> think?
>> Or, is there another, better suited (but similarly affordable) solution?
>>
>> Chanel widths: ~< 100 kHz
>> Time sampling: ~< millisecond
>> Polarisation: 2 channels
>> Antenna freq range: 10-85 MHz (total bandwidth of 75 MHz)
>> Digitisation: 14 bit
>>
>> Any advice on this would be great!
>>
>> Thanks in advance,
>> Colm
>> --
>>
>> *Dr Colm Bracken*
>> Lecturer
>> Maynooth University Experimental Physics
>>
>>
>> Maynooth University, Maynooth, Co. Kildare, Ireland.
>>
>> T: +353 1 708 3641
>> E: colm.brac...@mu.ie W: www.maynoothuniversity.ie
>>
>> Follow my work on https://nuim.academia.edu/ColmBracken
>>
>>
>>
>> And
>>
>>
>> Research Associate
>>
>> Astronomy & Astrophysics Section
>> School of Cosmic Physics
>> Dublin Institute for Advanced Studies
>> 31 Fitzwilliam Place
>> Dublin 2, D02 XF86
>>
>>
>>
>> T: +353 1 440 6656 ext 352
>> E: cbrac...@cp.dias.ie W: www.dias.ie/2017/06/22/dr-colm-bracken
>>
>> Follow my work on https://nuim.academia.edu/ColmBracken
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "casper@lists.berkeley.edu" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to casper+unsubscr...@lists.berkeley.edu.
>> To view this discussion on the web visit
>> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh8jNxeUnPGaSvwwuAtPCRsnNoCbOFnhbpU9EDb%2BPKh-Bg%40mail.gmail.com
>> 
>> .
>>
> --
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> casper@lists.berkeley.edu" group.
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> email to casper+unsubscr...@lists.berkeley.edu.
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> 

Re: [casper] Solar Spectrometer Channeliser

[Dan Werthimer]

hi colm,

regarding dynamic range
-
for your solar spectrometer, do you need 14 bits of ADC dynamic range?
it's very unusual in radio astronomy to need that much instantaneous
dynamic range on the input.
does the sun vary on short time scales in the radio band by factor of 1000
in voltage (1,000,000 in power) ?
or do you have very strong bursting RFI that is 1000 times the average
noise voltage (1M in power) in the whole band?

as you probably know, you'll have lots more dynamic range in the output
power spectrum than the dynamic range of the ADC:
if you are building a 1024 channel spectrometer with 1 ms integration,
you'll get about 8 bits more bits of dynamic range above your ADC dynamic
range in frequency domain voltage,
which is 16 bits more of dynamic range above your ADC dynamic range in
power spectra.
so you'll have about 20 bits of spectral dynamic range if you use an 8 bit
ADC,
(power spectrum dynamic range of about 1 million in 1 ms with an 8 bit ADC,
setting noise at 3 bit RMS).
and 24 bits of spectrral dynamic range for a 10 bit ADC, 28 bits for 12 bit
ADC, and 32 bits for for 14 bit ADC).

regarding boards for your spectrometer
---

1) as adam pointed out, the red pitaya is cheap, but sample rate and
bandwidth don't quite get the specs you need.

2)  another possibility is to use a snap board, which costs more, but can
sample 3 inputs at 950 Msps,
or 6 inputs at 500 Msps, or 12 inputs at 250 Msps with 8 bit ADC's.  most
people populate the snap board with 8 bit ADCs,
but a few people have populated it with 12 bit ADC's, although the sample
rate goes down by 8/12.

3) another possibility is to use a xilinx RFSOC board.  the first gen has a
bank of 12 bit ADC's  (8 inputs at 4 Gsps, or 16 inputs at 2 Gsps),
but i think the new generation has 14 bit ADC's ?the RFSOC boards cost
more than snaps, but RFSOC was designed
in dublin, so you can probably get one from xilinx dublin   the ZCU111
board has not been fully casperized yet though.

best wishes,

dan





Dan Werthimer
Marilyn and Watson Alberts Chair
Astronomy Dept and Space Sciences Lab
University of California, Berkeley


On Wed, Feb 5, 2020 at 5:06 AM Colm Bracken  wrote:

> Hello CASPER people,
>
> We are looking to build a spectrometer with not too demanding requirements.
> Based on the specs below, would the Red Pitaya be up to the job do you
> think?
> Or, is there another, better suited (but similarly affordable) solution?
>
> Chanel widths: ~< 100 kHz
> Time sampling: ~< millisecond
> Polarisation: 2 channels
> Antenna freq range: 10-85 MHz (total bandwidth of 75 MHz)
> Digitisation: 14 bit
>
> Any advice on this would be great!
>
> Thanks in advance,
> Colm
> --
>
> *Dr Colm Bracken*
> Lecturer
> Maynooth University Experimental Physics
>
>
> Maynooth University, Maynooth, Co. Kildare, Ireland.
>
> T: +353 1 708 3641
> E: colm.brac...@mu.ie W: www.maynoothuniversity.ie
>
> Follow my work on https://nuim.academia.edu/ColmBracken
>
>
>
> And
>
>
> Research Associate
>
> Astronomy & Astrophysics Section
> School of Cosmic Physics
> Dublin Institute for Advanced Studies
> 31 Fitzwilliam Place
> Dublin 2, D02 XF86
>
>
>
> T: +353 1 440 6656 ext 352
> E: cbrac...@cp.dias.ie W: www.dias.ie/2017/06/22/dr-colm-bracken
>
> Follow my work on https://nuim.academia.edu/ColmBracken
>
> --
> You received this message because you are subscribed to the Google Groups "
> casper@lists.berkeley.edu" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to casper+unsubscr...@lists.berkeley.edu.
> To view this discussion on the web visit
> https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAEx9wh8jNxeUnPGaSvwwuAtPCRsnNoCbOFnhbpU9EDb%2BPKh-Bg%40mail.gmail.com
> 
> .
>

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Re: [casper] Solar Spectrometer Channeliser

[Adam Isaacson]

Dear Colm,

I think you may find the bandwidth is the issue in this case. The Red
Pitaya (10 bit and 14 bit) seems to only have an input 50MHz (3dB)
bandwidth, so you would only get 10-50MHz bandwidth (total bandwidth of
40MHz). There is also a 16 bit version, but I suspect it has a similar
bandwidth, but docs are not that clear. We have only CASPERised the 10 bit
and 14 bit versions to date.

The info below may help:

Red Pitaya bandwidth info:
https://redpitaya.readthedocs.io/en/latest/developerGuide/125-14/fastIO.html
Red Pitaya spectrometer tutorial:
https://casper-tutorials.readthedocs.io/en/latest/tutorials/redpitaya/tut_spec.html

Maybe contact Nici Irimia at Red Pitaya and he will confirm the 16 bit
versions: nicu.iri...@redpitaya.com

I hope this helps.

Kind regards,

Adam Isaacson
South African Radio Astronomy Observatory (SARAO)
Hardware Manager
Cell: (+27) 825639602
Tel:  (+27) 215067300
email: aisaac...@ska.ac.za



On Wed, Feb 5, 2020 at 3:06 PM Colm Bracken  wrote:

> Hello CASPER people,
>
> We are looking to build a spectrometer with not too demanding requirements.
> Based on the specs below, would the Red Pitaya be up to the job do you
> think?
> Or, is there another, better suited (but similarly affordable) solution?
>
> Chanel widths: ~< 100 kHz
> Time sampling: ~< millisecond
> Polarisation: 2 channels
> Antenna freq range: 10-85 MHz (total bandwidth of 75 MHz)
> Digitisation: 14 bit
>
> Any advice on this would be great!
>
> Thanks in advance,
> Colm
> --
>
> *Dr Colm Bracken*
> Lecturer
> Maynooth University Experimental Physics
>
>
> Maynooth University, Maynooth, Co. Kildare, Ireland.
>
> T: +353 1 708 3641
> E: colm.brac...@mu.ie W: www.maynoothuniversity.ie
>
> Follow my work on https://nuim.academia.edu/ColmBracken
>
>
>
> And
>
>
> Research Associate
>
> Astronomy & Astrophysics Section
> School of Cosmic Physics
> Dublin Institute for Advanced Studies
> 31 Fitzwilliam Place
> Dublin 2, D02 XF86
>
>
>
> T: +353 1 440 6656 ext 352
> E: cbrac...@cp.dias.ie W: www.dias.ie/2017/06/22/dr-colm-bracken
>
> Follow my work on https://nuim.academia.edu/ColmBracken
>
> --
> You received this message because you are subscribed to the Google Groups "
> casper@lists.berkeley.edu" group.
> To unsubscribe from this group and stop receiving emails from it, send an
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